Handhole closure



Aug. 21, 1945. c. F. KRAMER ETAL 2,383,200

HANDHOLE CLO SURE Filed Feb. 12, 1943 Patented Aug. 21, 1945 HAN DHOLE CLOSURE Clarence F. Kramer, Birmingham, and Herbert F. Cromwell, Detroit, Mich., assignors to Ford Motor Company, Dearborn, Mich., a corporation of Delaware Application February 12, 1943, Serial No. 475,656

3 Claims.

This invention relates to closures; and, more particularly, to a handhole closure having particular utility in connection with airframe construction.

T'he article described in this specification is a removable cover and its supporting flange designed to be incorporated into the skin construction of either the fuselage or wings of aircraft to provide access openings for inspection or adjustment of the structure therein. An advantage of the article made according to this invention is that it combines extreme lightness of weight with a faired outer surface and a readily removable yet absolutely secure locking device. Another advantage is that it offers a simpliedmeans of installing the closure, particularly on fabric components so that it may be secured in place with` out initially cutting a hole in the fabric, and thus it does not permit fabric distention, which otherwise occurs when conventional closures are used. Another advantage is that locking means are provided Which prevent loosening of the device or rattling in operation and which are readily incorporated in the article in the course of manufacture. Yet another advantage is that but two elements are required, each being of integral construction and beingreadily molded so that the saving in manufacturing cost as measured against the built-up construction heretofore used is considerable.

With these and other objects in view, the invention consists of the arrangement, construction and combination of the various parts of 'the improved device, as described in the specification, claimed in the claims and illustrated in the accompanying drawing in which:

Figure 1 is a plan view of the flange and closure, a portion of each element being broken away to show internal construction.

Figure 2 is a sectional view taken on the line 2-2 of Figure 1, and it shows a method of installing the closure on a fabric airframe surface.

Figure 3 is an elevation on an enlarged scale of the closure.

Figure 4 is a partial section corresponding to Figure 2, showing the method of attachment of the device to a metallic airframe component.

Referring to Figure 1, the preferred form of the invention comprises a flange I IJ and a disc closure II, both of which are preferably molded from a plastic material, although, as it will appear later,

the flange may, in some instances. be formed of metal. The flange I Il, as best shown in section in Figure 2, tapers outwardly and has a narrow inwardly extending ring I2 about its inner opening,

the base I3 of the ring I2 being flush with the base I4 of the flange IIJ and the top I5 of the ring being spaced a different distance below the top of the flange. At intervals, in this case of the ring I2 is extended inwardly a short distance to form locking lugs I6 which may be formed with a central depression I'I on the top surface and a complementary extension I8 on the bottom surface, as best seen in Figure 3.

The closure I I is essentially a disc I Si having finger holes 20 inset from its upper surface and a continuous depending skirt 2| spaced a short dif'- tance inwardly from the outer circumference of the disc and on the lower side thereof. At intervals, corresponding to those of the lug arrangement on the flange, the skirt 2l is extended radially outwardly adjacent its lower edge forming ridges 22. This is best shown in Figure 3 in which it will be noted that the upper surface of the ridge 22 has an initial sloping section 23 extending upwardly from the bottom surfaceof the skirt, a shoulder 24 and a parallel section 25 forming a retaining chamber 26 having the end wall 35. About midway of this chamber and on the lower surface of the disc II, a detent 21 is formed, extending downwardly into the retaining chamber 26. It will be apparent that the entire closure element may be molded in one piece and no auxiliary retainers or springs are required.

In operation, the closure II is aligned with the flange I0 so that the lugs I6 on the flange are located between the spaced ridges 22 of the closure. The closure is then moved inwardly until the undersurface of the disc rests against the top I5 of the ring I2. The closure is then rotated in a clockwise direction, each lug I6 sliding upwardly on the sloping section 23 of each ridge 22 until it passes the shoulder 24 and then falls into the retaining chamber 26. While in this chamber, as shown in Figure 3, the detent 21 bears against corresponding depression I'I in the lug and securely locks the device in its assembled condition, the lug I6 being slightly iiexed in passing between the shoulder and the detent.

The preferred method of assembling the flange g thus securing the flange in position. The Vfabric defined by the inner edge of the ange opening is then cut out with a sharp knife, the bottom surface of the flange and of the lugs I 6, as shown in Figure 2 at 29, being left covered with the fabric. However, by initially gluing the flange to the uncut stretched fabric, the fabric does not have a chance to distend when the hole is finally cut, as it is then supported throughout by the flange itself.

To accomplish this assembly satisfactorily, Drovision should be made in the spacing between the upper surface of ridges 22 and the underside of the disc I9 to allow for the additional thickness of the fabric at 29. It willbe noted that this structure may be applied entirelyfrom the outside of the plane and at any time in the course of construction after the fabric covering is in place. It may be applied with equal ease when the craft is in actual service without respect to the fact that the position may be inaccessible from the interior ofthe ship, which is usually the case, as otherwise it would not be necessary to provide these inspection means. To complete the assembly, a reinforcing ring 30 of fabric generally applied substantially covers the exterior portion of the flange Ill and extends over about an equal radialdistance on the fabric of the structure. This is doped in place and thoroughly secures the assembly.

Provision may also be made for attaching this closure to metallic structure such as shown in Figure 4, in which case the flange 3| is made from aluminum and either riveted, as shown in 32, or welded, as indicated at 33, in position on the skin Il. This may be done quite simply as the flange is a relatively easy part to produce in metal and the closure itself may still be cast plastic, as it would be rather dimcult to fabricate in any-metal which would have the requisite resiliency and lightness.

Some changes may be made in the arrangement, construction and combination of the various parts of the improved device without departing from the spirit of the invention, and it is the intention to cover by the claims such changes as may reasonably be included within the scope thereof.

The invention claimed is:

1. In a handhole closure, a molded plastic ring flange having internally directed lugs, the bottom surfaces of said ange and said lugs being substantially coplanar, a molded plastic disc-shaped closure adapted to be received centrally of said flange, depending means on said closure adjacent the circumference thereof having radially outwardly extending portions spaced from said disc forming retaining chambers closed at vone end corresponding to the spacing of said lugs, the circumferential length of said chambers being substantially equivalent to the length of said lugs, said lugs being received in said retaining chambers between said disc and said extending portions, a shoulder at the other end of each said chamber on said extending portion, and an integral projecting boss formed on the lower Side of said disc substantially midway of said chamber adapted to flex said lug passing between said shoulder and said boss.

2. In a handhole closure, a ring flange formed of molded plastic' material having a substantially uniform width with spaced substantially flat lugs formed integrally therewith and extending radially inwardly therefrom adjacent to the bottom surface thereof, a disc closure formed of molded plastic material adapted to be centrally receivedV in said ange and having spaced circumferentiallyv extending retaining chambers formed integral therewith and therebeneath and having a rooi and a floor opening outwardly, said chambers adapted to receive said lugs and being approximately equal in length thereto, corresponding ends of said chambers being closed, the opposite ends of said chambers having a shoulder formed adjacent the floor thereof, inclined surfaces leading to said chambers at said shoulders, a projection formed on said roof substantially midway of each of said chambers, said shoulder and said projection being so spaced that said lug in passing therebetween is flegied thereby and is locked in said chamber.

3. The structure of claim 2 which is further characterized in that said closure being adapted for installation on stretched fabric aircraft skin, said lugs and said ring have substantially co4 planar bases, and said chambers are proportioned to receive said lugs with a thickness of fabric skin adhering to the lower surface thereof.

CLARENCE F. KRAMER. HERBERT F. CROMWELL. 

